Actuator driver

ABSTRACT

A position detection unit generates a position detection value P FB  that indicates the position of a control target. A temperature detection unit generates a temperature detection value that indicates the temperature. A correction unit corrects the position detection value P FB . A controller generates a control instruction value S REF  such that the position detection value P FB   _   CMP  subjected to the correction matches a position instruction value P REF  that indicates the target position of the control target. A driver unit applies a driving signal that corresponds to the control instruction value S REF  to an actuator. The correction unit corrects the position detection value P FB  such that the relation between the position detection value P FB  and the actual position exhibits linearity that is uniform independent of the temperature.

CROSS REFERENCE TO RELATED APPLICATION

The present invention claims priority under 35 U.S.C. §119 to JapaneseApplication No. 2017-118635, filed Jun. 16, 2017 and JapaneseApplication No. 2016-198760, filed Oct. 7, 2016, the entire content ofwhich is incorporated herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to an actuator driver, a lens controlapparatus, and an image capture apparatus employing the lens controlapparatus.

Description of the Related Art

In recent years, with camera modules to be mounted on a smartphone orthe like, an increasing number of such camera modules have a function ofdetecting the position of an image capture lens, and of controlling theposition of the image capture lens with high speed and high precision byfeeding back the position information thus detected. By employing such afeedback control operation for an autofocus operation, this enables ahigh-precision, high-speed autofocus operation. Also, by employing sucha feedback control operation for optical image stabilization (OIS), thisenables high-precision image stabilization. With cameras employing sucha feedback control operation, in a case in which the position detectionsignal varies due to temperature, in some cases, this leads to theoccurrence of control error. Typical OIS is designed as a linear controloperation. Accordingly, it is important to secure linearity between theposition detection signal and the actual position.

In particular, with image capture apparatuses that include an imagesensor having a phase difference detection function in order to supportan autofocus operation, the position of the image capture lens isdirectly changed up to the position indicated by the output value of aposition detection signal that corresponds to the focal positionestimated based on the phase difference detection, thereby providing ahigh-speed autofocus operation. In a case in which deviation occurs inthe relation between the focal position and the output value of theposition detection signal due to a change in temperature, this leads toaccessing a position that deviates from the focal position. Thisrequires additional time for focusing. Also, such an arrangementdisplaces the image capture lens to a target position assuming thatthere is a linear relation between the target position and the positiondetection signal. Accordingly, in a case in which deviation occurs inthe linearity between the position detection signal and the change inposition, this also leads to accessing a position that deviates from thefocal position. As described above, with such an image capture apparatusincluding an image sensor having a phase difference detection function,it is important to support both temperature compensation and linearitycompensation.

Also, with an image capture apparatus including multiple camera modules,which is referred to as a “dual camera” or the like, in some cases,there is a need to perform control so as to interlink the operations ofthe multiple camera modules. With such an arrangement, in a case inwhich deviation due to temperature occurs in the relation between theposition detection signal and the actual position, this leads todeviation in the interlinking between the two camera modules. In somecases, this leads to adverse effects on image generation. Also, in acase in which deviation has occurred in the linearity of the relationbetween the position detection signal and the change in position, thisleads to deviation in the interlinking between them. In some cases, thisalso leads to adverse effects on image generation. As described above,in such an image capture apparatus including multiple camera modules, itis also important to support both temperature compensation and linearitycompensation.

A driving apparatus is described in Patent document 1 (WO 2009/093645),configured to detect the surrounding temperature based on a resistancevalue of a shape memory alloy member, and to correct the slope componentand the offset component of the relation between the control value andthe change in position characteristic based on the difference betweenthe surrounding temperature and the reference temperature. A controlcircuit is described in Patent document 2 (Japanese Patent ApplicationLaid Open No. 2009-145635), configured to perform correction based on acorrection function stored beforehand such that the output signal of theposition detector exhibits linearity.

In Patent document 1, temperature compensation is described in which thesurrounding temperature is detected based on the resistance value of ashape memory alloy member, and the slope component and the offsetcomponent of the relation between the control value and the change inposition characteristic are corrected based on the difference betweenthe surrounding temperature and a reference temperature. However, therelation between the control value and the change in positioncharacteristic is derived based on factory measurement values of twoparticular positions and the corresponding control values. Specifically,the relation between the control value and the change in positioncharacteristic is derived by defining a straight line that passesthrough the two positions. Thus, such temperature compensation by nomeans supports a case in which there is a nonlinear relation betweenthem.

In Patent document 2, linearity compensation is described in whichcorrection is performed based on a correction function stored beforehandsuch that the output signal of the position detector exhibits linearity.However, such linearity compensation by no means supports a change incharacteristics due to a change in temperature.

SUMMARY OF THE INVENTION

The present invention has been made in view of such a situation.Accordingly, it is an exemplary purpose of an embodiment of the presentinvention to provide a lens control apparatus that supportshigh-precision, high-speed positioning of an image capture lens.

An embodiment of the present invention relates to a lens controlapparatus. The lens control apparatus comprises: a lens; an actuatorstructured to position the lens; a Hall element structured to generate aposition detection signal that indicates the position of the lens; atemperature detection unit structured to detect a temperature based on avoltage across the Hall element in a state in which a constant currentis applied to the Hall element; and a control unit structured to controlthe actuator such that the position detection signal approaches aposition instruction signal that indicates a target position of thelens.

With this embodiment, the temperature can be detected based on thechange in an internal resistance of the Hall element, which is providedprimarily as a position detector. Accordingly, such an embodiment doesnot require an additional temperature sensor, thereby allowing therequired costs and circuit space to be reduced. Furthermore, such anembodiment is capable of detecting the temperature and the positionbased on the changes in voltages across the different terminals. Thissupports the temperature detection and the position detection in aparallel and/or continuous manner.

Also, the control unit may comprise a temperature compensation unitstructured to correct a temperature dependence of a relation between theposition detection signal and a corresponding actual position of thelens.

By using the temperature detected by means of the Hall element tocorrect the temperature characteristics of the Hall element itself, thisprovides high-precision temperature compensation.

Also, the control unit may further comprise a linearity compensationunit structured to correct a linearity of the relation.

By performing the temperature compensation and the linearitycompensation in the position control operation for the lens, thisprovides high-precision and high-speed positioning.

Also, the relation may be acquired at a predetermined temperature. Also,the control unit may further comprise a memory structured to storeinformation with respect to the relation. Also, the linearity may becorrected for a current temperature that differs from the predeterminedtemperature, based on the relation acquired at the predeterminedtemperature. Also, temperature compensation may be performed with apredetermined correction coefficient supplied according to a differencebetween the predetermined temperature and the current temperature.

This embodiment employs the relation between the position detectionsignal and the change in position of the lens acquired at apredetermined temperature, and the correction coefficient thatcorresponds to the difference between the predetermined temperature andthe current temperature. Thus, such an embodiment requires only a smallmemory capacity and only a small amount of calculation to support boththe temperature compensation and the linearity compensation.

Also, the relations may be acquired for multiple predeterminedtemperatures. Also, the control unit may further comprise a memorystructured to store information with respect to the relations. Also, thelinearity may be corrected for a current temperature that differs fromthe predetermined temperatures, based on the relation acquired for onefrom among the multiple temperatures that is closest to the currenttemperature. Also, temperature compensation may be performed such thatthe relation is represented by a straight line having a slope that isunrelated to the temperature.

This embodiment employs multiple relation expressions for the respectivepredetermined temperatures. This provides the temperature compensationand the linearity compensation with improved precision. Furthermore,this allows limitation of the number of predetermined temperatureconditions for which the relation is to be measured beforehand. Thisallows the required memory capacity to be reduced.

Also, the relations may be acquired for multiple predeterminedtemperatures. Also, the control unit may further comprise a memorystructured to store information with respect to the relations. Also, therelation may be generated for the current temperature based on therelations acquired for adjacent temperatures between which the currenttemperature is positioned, from among the multiple predeterminedtemperatures. Also, linearity compensation may be performed based on therelation thus generated. Also, temperature compensation may be performedsuch that the relation is represented by a straight line having a slopethat is unrelated to the temperature.

This embodiment employs multiple relation expressions for the respectivepredetermined temperatures. This provides the temperature compensationand the linearity compensation with improved precision. Furthermore,this allows limitation of the number of predetermined temperatureconditions for which the relation is to be measured beforehand. Thisallows the required memory capacity to be reduced.

Another embodiment of the present invention relates to an image captureapparatus. The image capture apparatus may comprise: any one of the lenscontrol apparatuses; and an image sensor that is capable of performingphase difference detection in order to support an autofocus controloperation. Temperature compensation and linearity compensation areemployed in detection of the position of the lens in order to support anautofocus control operation.

Such an arrangement is capable of directly accessing the target focalposition by means of phase difference detection based on the positiondetection signal subjected to the temperature compensation and thelinearity compensation. This provides high-speed and high-precision lenspositioning.

Yet another embodiment of the present invention also relates to an imagecapture apparatus. The image capture apparatus may comprise multiplecamera modules. Also, each camera module may comprise any one of theaforementioned lens control apparatuses. Also, temperature compensationand linearity compensation may be employed in detection of the positionof the lens in order to support an autofocus control operation for eachcamera module.

Such an arrangement is capable of driving the multiple lenses of therespective camera modules in an interlinked manner. Furthermore, theposition detection signal is corrected for the change in temperature.This allows interlinking of the multiple camera modules in a state as ifthere was no change in temperature.

Yet another embodiment of the present invention relates to an actuatordriver. The actuator driver comprises: a position detection unitstructured to generate a position detection value that indicates theposition of a control target, based on a Hall signal generated by a Hallelement; a correction unit structured to correct the position detectionvalue; a controller structured to generate a control instruction valuesuch that the position detection value subjected to correction matches aposition instruction value that indicates a target position of thecontrol target; a driver unit structured to apply a driving signal thatcorresponds to the control instruction value to an actuator; and atemperature detection unit structured to generate a temperaturedetection value that indicates the temperature based on a voltage acrossthe Hall element in a state in which a predetermined current is suppliedto the Hall element.

With this embodiment, the temperature can be detected based on thechange in the internal resistance of the Hall element, which is providedprimarily as a position detector. Accordingly, such an embodiment doesnot require an additional temperature sensor, thereby allowing therequired costs and circuit space to be reduced. Furthermore, such anembodiment is capable of detecting the temperature and the positionbased on the changes in voltages across the different terminals. Thissupports the temperature detection and the position detection in aparallel and/or continuous manner.

Also, the correction unit may be structured to correct the positiondetection value such that the relation between the position detectionvalue and an actual position exhibits a linearity that is uniformindependent of the temperature.

With this embodiment, by performing the temperature compensation and thelinearity compensation in the position control operation for the controltarget, this provides high-precision and high-speed positioning.

Also, the position detection value may be corrected such that therelation between the position detection value and an actual position isuniform regardless of the temperature in a range in the vicinity of theposition of the control target that corresponds to a predeterminedposition detection value.

Also, with the position detection value or otherwise the positioninstruction value as y, with the actual position as x, and with therelation between x and y as an x−y characteristic, the correction unitmay comprise memory structured to store data that represents the x−ycharacteristic y=a*x+b generated in the form of a linear function to beused as a calculation target, data that represents a function x=f(y)obtained by means of a polynomial approximation of the x−ycharacteristic measured beforehand at a predetermined temperature, andcorrection coefficients c and d (d may be set to zero) acquired for eachof multiple temperatures. Also, the correction unit may be structured toperform an operation comprising: calculating x₁=f(y₁) with the positiondetection value received from the position detection unit as y₁;calculating y₂=a*x₁+b; determining the coefficients c and d thatcorrespond to the temperature indicated by the temperature detectionvalue; and calculating y₃=c*y₂+d. Also, y₃ may be employed as theposition detection value subjected to correction.

Also, the function x=y(y) may be divided into multiple sections. Also,the function may be approximated for each section in the form of alinear function.

This allows the calculation time and the memory capacity required forintermediate calculation to be reduced as compared with an arrangementin which the relation is approximated over the overall range by means ofa single common higher-order function.

In a step for determining the coefficients c and d that correspond tothe temperature (detection temperature) indicated by the temperaturedetection value, (i) the correction coefficients defined for atemperature that is closest to the detection temperature may beselected. Also, (ii) the correction coefficients may be derived by meansof calculation such as interpolation, averaging, or the like, based onthe correction coefficients defined for two temperatures between whichthe detection temperature is positioned.

Also, with the position detection value or otherwise the positioninstruction value as y, with the actual position as x, and with therelation between x and y as an x−y characteristic, the correction unitmay comprise memory structured to store data that represents the x−ycharacteristic y=a*x+b generated in the form of a linear function to beused as a calculation target, and data that represents a functionx=f₀(y), x=f₁(y), and the like, obtained by means of a polynomialapproximation of x−y characteristics measured beforehand at multiplepredetermined temperatures T₀, T₁, and the like. Also, the correctionunit may be structured to perform an operation comprising: determining afunction x=f′(y) that corresponds to the temperature indicated by thetemperature detection value; calculating x₁=f′(y₁) with the positiondetection value received from the position detection unit as y₁; andcalculating y₂=a*x₁+b. Also, y₂ may be employed as the positiondetection value subjected to correction.

Also, the function x=y′(y) may be divided into multiple sections. Also,the function may be approximated for each section in the form of alinear function.

This allows the calculation time and the memory capacity required forintermediate calculation to be reduced as compared with an arrangementin which the relation is approximated over the overall range by means ofa single common higher-order function.

In a step for determining the function x=f′(y) that corresponds to thetemperature (detection temperature) indicated by the temperaturedetection value, (i) a function defined for a temperature that isclosest to the detection temperature may be selected. Also, (ii) such afunction may be derived by means of calculation such as interpolation,averaging, or the like, based on the functions defined for twotemperatures between which the detection temperature is positioned.

Also, the actuator may be monolithically integrated on a singlesemiconductor substrate.

Yet another embodiment of the present invention relates to a lenscontrol apparatus. The lens control apparatus may comprise: a lens; anactuator comprising a movable portion on which the lens is mounted; andany one of the aforementioned actuator drivers structured to drive theactuator.

Yet another embodiment of the present invention relates to an imagecapture apparatus. The image capture apparatus may comprise: an imagesensor; and the aforementioned lens control apparatus.

It should be noted that any combination of the aforementionedcomponents, any component of the present invention, or any manifestationthereof, may be mutually substituted between a method, apparatus,system, and so forth, which are also effective as an embodiment of thepresent invention.

It is to be noted that any arbitrary combination or rearrangement of theabove-described structural components and so forth is effective as andencompassed by the present embodiments. Moreover, this summary of theinvention does not necessarily describe all necessary features so thatthe invention may also be a sub-combination of these described features.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described, by way of example only, withreference to the accompanying drawings which are meant to be exemplary,not limiting, and wherein like elements are numbered alike in severalFigures, in which:

FIG. 1 is a diagram showing an image capture apparatus;

FIG. 2 is a flowchart showing operations for temperature compensationand linearity compensation employed in a lens control apparatusaccording to a first embodiment of the present invention;

FIG. 3 is a diagram for explaining a method for calculating the slopethat represents the relation between the position detection signal andthe change in position, which is required to perform the linearitycompensation;

FIG. 4 is a diagram for explaining a method for calculating the slopeand the offset that represent the relation between the positiondetection signal and the change in position, which is required toperform the linearity compensation;

FIG. 5 is a diagram showing measurement results for explaining thechange in the relation between the position detection signal and thechange in position due to temperature;

FIG. 6 is a diagram showing the results obtained by performing thelinearity compensation for the measurement results of the relationsbetween the position detection signal and the change in positionacquired for respective temperatures shown in FIG. 5;

FIG. 7 is a diagram showing the results obtained by further performingthe temperature compensation for the results subjected to the linearitycompensation shown in FIG. 6;

FIG. 8 is a diagram showing the results obtained by performing thetemperature compensation using an average value of optimum correctioncoefficients defined for respective multiple lens control apparatuses asa common correction coefficient instead of the correction coefficientemployed in the temperature compensation shown in FIG. 7;

FIG. 9 is a diagram showing the results obtained by performing thetemperature compensation by means of slope correction before performingthe linearity compensation;

FIG. 10 is a flowchart showing the operations for the temperaturecompensation and the linearity compensation employed in the lens controlapparatus according to a second embodiment of the present invention;

FIG. 11 is a diagram showing the results obtained by performing thelinearity compensation for the measurement results acquired for multipletemperatures based on the relation between the position detection signaland the change in position acquired for the respective temperaturesshown in FIG. 5, and by performing the temperature compensation suchthat the slope does not change due to temperature;

FIG. 12 is a diagram showing the measurement results for explaining thechange in the relation between the position detection signal and thechange in position due to temperature, in a lens control apparatushaving a relation that is different from that shown in FIG. 5;

FIG. 13 is a diagram showing the results obtained by performing slopecorrection and offset correction as the temperature compensation for themeasurement results shown in FIG. 12 before performing the linearitycompensation;

FIG. 14 is a diagram showing the results obtained by performing thelinearity compensation for the measurement results acquired for multipletemperatures based on the relations between the position detectionsignal and the change in position acquired for the respectivetemperatures based on the results shown in FIG. 13, and by performingthe temperature compensation such that the slope does not change due totemperature;

FIG. 15 is a flowchart showing the operations for the temperaturecompensation and the linearity compensation employed in a lens controlapparatus according to a third embodiment of the present invention;

FIG. 16 is a diagram showing the results obtained by performing thelinearity compensation and the temperature compensation after the strokerange has been limited;

FIG. 17 is a diagram for explaining linear approximation of the functionaccording to a fourth embodiment;

FIG. 18 is a block diagram showing a system configuration of the lenscontrol apparatus; and

FIG. 19 is a diagram showing the temperature dependence of theresistance value of a Hall element.

DETAILED DESCRIPTION OF THE INVENTION

The invention will now be described based on preferred embodiments whichdo not intend to limit the scope of the present invention but exemplifythe invention. All of the features and the combinations thereofdescribed in the embodiment are not necessarily essential to theinvention.

In some cases, the sizes (thickness, length, width, and the like) ofeach component shown in the drawings are expanded or reduced asappropriate for ease of understanding. The size relation betweenmultiple components in the drawings does not necessarily match theactual size relation between them. That is to say, even in a case inwhich a given member A has a thickness that is larger than that ofanother member B in the drawings, in some cases, in actuality, themember A has a thickness that is smaller than that of the member B.

In the present specification, the state represented by the phrase “themember A is coupled to the member B” includes a state in which themember A is indirectly coupled to the member B via another member thatdoes not substantially affect the electric connection between them, orthat does not damage the functions or effects of the connection betweenthem, in addition to a state in which they are physically and directlycoupled.

Similarly, the state represented by the phrase “the member C is providedbetween the member A and the member B” includes a state in which themember A is indirectly coupled to the member C, or the member B isindirectly coupled to the member C via another member that does notsubstantially affect the electric connection between them, or that doesnot damage the functions or effects of the connection between them, inaddition to a state in which they are directly coupled.

Description will be made in the present embodiment regarding an actuatordriver that drives an actuator that performs positioning of a lens.First, brief description will be made regarding a configuration of anactuator that moves an image capture lens. FIG. 1 is a diagram showingan image capture apparatus. An image capture apparatus 300 is configuredas a camera module built into a digital still camera, digital videocamera, smartphone, or a tablet terminal. An image capture apparatus 300includes an image sensor 302, a lens 304, a processor 306, and a lenscontrol apparatus 400. The lens 304 is arranged on an optical axis oflight to be input to the image sensor 302. For example, the lens 304 maybe an autofocus (AF) lens or an image stabilization lens. The lenscontrol apparatus 400 performs positioning of the lens 304 based on aposition instruction value (which will also be referred to as a “targetcode”) P_(REF) received from the processor 306.

For example, in a case in which the lens 304 is configured as an AFlens, the lens control apparatus 400 is configured to change theposition of the lens 304 in the optical axis direction (Z direction).The processor 306 generates the position instruction value P_(REF) suchthat the captured image has high contrast (contrast AF). Alternatively,the position instruction value P_(REF) may be generated based on theoutput of an AF sensor provided as an external component of the imagesensor 302 or otherwise an AF sensor embedded in an image capture face(phase difference AF).

In a case in which the lens 304 is configured as an image stabilizationlens, the lens control apparatus 400 changes the position of the lens304 in the X-axis direction and/or in the Y-axis direction in a planedefined in parallel with the image sensor 302. The processor 306generates the position instruction value P_(REF) based on the outputfrom a gyro sensor.

Description will be made below assuming that the lens 304 is configuredas an AF lens.

The lens control apparatus 400 controls the actuator 402 by means of aposition feedback control operation. Specifically, the lens controlapparatus 400 includes an actuator 402, a position detector 404, atemperature detector 406, and an actuator driver IC (Integrated Circuit)500. The actuator 402 is configured as a voice coil motor, for example.A movable portion of the voice coil motor is coupled to a holder 308 forthe lens 304. A stationary portion of the voice coil motor is fixedlymounted on a housing of the image capture apparatus 300.

In many cases, the position detector 404 employs a magnetic detectionmeans such as a Hall element or the like. Description will be made belowassuming that such a Hall element is employed. A permanent magnet ismounted on the movable portion of the voice coil motor. A Hall elementis mounted on the stationary portion thereof. When a relative changeoccurs in the positions of the movable portion and the stationaryportion, the magnetic flux input to the Hall element changes. The Hallelement generates an electric signal (which will be referred to as the“position detection signal P_(FB)” hereafter) that corresponds to thechange in the input magnetic flux, i.e., the change in position of theactuator 402, and in other words, the current position of the lens 304.The position detection signal P_(FB) is fed back to the actuator driverIC 500.

The actuator driver IC 500 is configured as a function IC integrated ona single semiconductor substrate. Examples of such an “integrated”arrangement include: an arrangement in which all the circuit componentsare formed on a semiconductor substrate; and an arrangement in whichprincipal circuit components are monolithically integrated. Also, a partof the circuit components such as resistors and capacitors may bearranged in the form of components external to such a semiconductorsubstrate in order to adjust the circuit constants. By integrating thecircuit on a single chip, such an arrangement allows the circuit area tobe reduced, and allows the circuit elements to have uniformcharacteristics.

The actuator driver IC 500 feedback controls the actuator 402 such thatthe position detection signal P_(FB) thus fed back matches the positioninstruction value P_(REF).

As described above, the position of the lens 304 is detected and used asfeedback data for the position control operation. This suppressestransient oscillation in the step response, thereby providing high-speedsettling. Also, this provides high-speed access to the target position.

Ideally, such an arrangement preferably has a relation (which will bereferred to as the “x−y characteristic” hereafter) having linearity withno irregularities and no variation regardless of changes in temperatureor the like, between the actual position of the lens 304 (actuator 402)(which will be referred to as a “variable x” hereafter) and the outputof the position detector 404 (i.e., the position detection signalP_(FB)) or otherwise the corresponding position instruction valueP_(REF) (which will also be referred to as a “variable y” hereafter).However, in actuality, the x−y characteristic is a nonlinear relation.Furthermore, the x−y characteristic varies for every image captureapparatus 300. Moreover, such a relation (x−y characteristic) varies dueto the temperature of the position detector 404. Accordingly, in a casein which this relation (x−y characteristic) varies, the actual positionof the lens 304 deviates even if the control operation is performed suchthat the position detection signal P_(FB) matches the positioninstruction value P_(REF).

The actuator driver IC 500 has a function of correcting the x−ycharacteristic as described later in detail. In order to support such acorrection function, the temperature detector 406 is provided. Thetemperature detector 406 detects the temperature of the positiondetector 404. It should be noted that, in a case in which thetemperature of the position detector 404 matches the surroundingtemperature, or otherwise, in a case in which there is a strongcorrelation between them, the temperature detector 406 may measure thesurrounding temperature. The temperature information T thus detected isinput to the actuator driver IC 500. The actuator driver IC 500 correctsthe driving control operation of the actuator 402 based on thetemperature information T. The temperature detector 406 may be athermistor, posistor, thermocouple, or the like. Alternatively, in acase in which the position detector 404, for which the temperaturedetection is to be performed, is configured as a Hall element, the Hallelement itself may be employed as the temperature detector 406.

Most strictly, the following flow provides a control operation withoutindividual variation and without variation due to temperature.

1. Before shipping, the relation (x−y characteristic) between theposition detection signal y and the actual position x is measured foreach of multiple temperatures.

2. The change in position (or position) that corresponds to the positiondetection signal is acquired with reference to one relation thatcorresponds to the current temperature from among the multiple relationsmeasured beforehand.

However, such a flow requires an enormous amount of detection timebefore shipping. Furthermore, it is necessary to hold, in an internalcomponent of the actuator driver IC, the x−y characteristics formultiple respective temperatures. Accordingly, such an arrangementrequires large-capacity memory. In particular, in a case in which thex−y characteristics exhibit a non-linear relation, this problem becomesserious.

Description will be made below with reference to the first embodimentthrough the third embodiment regarding a correction operation thatrequires only a small memory capacity to allow a control operation to beperformed while suppressing individual variation and variation due totemperature. The correction operation that will be described below canbe roughly classified into two compensation operations. That is to say,one is linearity compensation that provides a linear relation betweenthe position detection signal (position instruction value) and theactual position, and the other is temperature compensation that correctsvariation due to temperature.

First Embodiment

Description will be made with reference to FIGS. 2 through 9 regardingthe first embodiment of the present invention. FIG. 2 is a flowchartshowing a temperature compensation operation and a linearitycompensation operation employed in the first embodiment of the lenscontrol apparatus according to the present invention. FIG. 3 is adiagram for explaining a method for calculating the slope thatrepresents the relation between the position detection signal and thechange in position, which is required for the linearity compensation.FIG. 4 is a diagram for explaining a method for calculating the slopeand the offset that represent the relation between the positiondetection signal and the change in position, which is required for thelinearity compensation. FIG. 5 shows measurement results for explainingthe change in the relation between the position detection signal and thechange in position due to temperature. FIG. 6 is a diagram showingresults of the linearity compensation performed for the measurementresults of the relations between the position detection signal and thechange in position for the respective temperatures in FIG. 5. FIG. 7 isa diagram showing the results of the temperature compensation furtherperformed for the results obtained by the linearity compensation shownin FIG. 6. FIG. 8 is a diagram showing the results of the temperaturecompensation using the average of optimum correction coefficientsdesigned for the respective multiple lens control apparatuses as acorrection coefficient, instead of the correction coefficients employedin the temperature compensation shown in FIG. 7. FIG. 9 is a diagramshowing the results of temperature compensation by means of slopecorrection before the linearity compensation is performed.

Description will be made with reference to FIG. 2 regarding the overalloperation of the linearity compensation and the temperaturecompensation. In the first embodiment, the linearity compensation isperformed for each temperature using the relation between the positiondetection signal and the change in position at a single predeterminedtemperature.

The operations 1 through 3 are performed in an inspection step beforeshipping after the image capture apparatus 300 is manufactured. In theoperation 1, the relation (x−y characteristic) between the positiondetection signal y (position detection value P_(FB) shown in FIG. 1) andthe change in position x at a predetermined temperature (which will alsobe referred to as the “reference temperature”) T₀, e.g., the settemperature of the manufacturing factory. The position detection signaly may be an output voltage of the Hall element. In a case in which themeasurement is performed while driving a servo motor, the positiondetection signal y may be a target code (position instruction valueP_(REF) shown in FIG. 1). The reason is as follows. That is to say, thetarget code is a code that indicates the position of the target to beaccessed. After the position is settled to the target position by meansof the servo motor, the target code is equivalent to the output voltageof the Hall element. The change in position x may be directly measuredas the change in position of the image capture lens by means of a laserdisplacement meter or the like. The relation between the positiondetection signal y and the change in position x thus measured does notnecessarily exhibit linearity. Furthermore, it is conceivable that therelation would change due to a change in the temperature from T₀. Theoperation 1 is performed for all individual products.

In the operation 2, a linear function y=a * x +b is designed. The slope“a” and the intercept “b” are preferably designed giving considerationto the x−y characteristic obtained in the operation 1. For example, byperforming linear approximation of the x−y characteristic, the slope “a”and the intercept “b” may be derived. It should be noted that such alinear function y=a * x +b may be designed independently of the x−ycharacteristic at the reference temperature T₀.

In a case in which zero-point adjustment is performed in themeasurement, the x−y characteristic in the measurement result passesthrough the origin, i.e., b=0. Thus, such an arrangement requires onlythe slope “a” to be derived. For example, as shown in FIG. 3, themeasurement result is represented in the form of a function y=g(x).After the function g(x) is differentiated, the slope of the function ata position x₀ in the vicinity of the center of the stroke can becalculated as represented by a=g′(x₀). That is to say, the functiony=a*x is designed as a linear function 7 having the slope a and passingthrough the origin. On the other hand, in a case in which themeasurement result is represented by a linear function that does notpass through the origin, an offset calculation (b≠0) may be performed soas to shift the measurement result such that it can be represented by alinear function that passes through the origin. Also, as shown in FIG.4, the function y=a*x+b may be designed as represented by a linearfunction 9 that passes through two desired positions of the measurementresult 8, e.g., both ends of the practical stroke range, andspecifically, (x₀₁, y₀₁) and (x₀₂, y₀₂).

In the operation 3, the relation between the position detection signal yand the change in position x (x−y characteristic) measured in theoperation 1 is represented in the form of a function. In an actualmachine such as a cellular phone, y represents a measurement value.Accordingly, a function such as x=f(y) is designed with y as a variable,so as to represent the measurement result. In order to fit a nonlinearrelation, the function is required to have a second order or more(polynomial approximation). As the polynomial order is raised, thefitting error becomes smaller. However, this involves an increase in thecalculation amount. Accordingly, the order may preferably be designedaccording to the actual conditions. Description will be made belowregarding linearity compensation employing a fifth-order function.

x=y(y)=k ₀+(k ₁ *y)+(k ₂ *y ²)+(k ₃ *y ³)+(k ₄ *y ⁴)+(k ₅ *y ⁵)   (1)

The operations 4 through 6 are performed in an actual operation of theactuator driver IC 500. Description will be made below with the positiondetection signal y acquired from the position detector 404 in the actualoperation as y₁.

In the operation 4, the position detection signal y₁ detected in theactual measurement is assigned to the function expression (1) so as toacquire the calculated change in position x₁. The change in position x₁is a tentative value.

x₁=f(y₁)

In a case in which the surrounding temperature is equal to T₀, it isassumed that the measurement result matches the factory measurementresult. In a case in which the surrounding temperature T₁ is differentfrom T₀, the function x=f(y) derived for T₀ is also employed. It shouldbe noted that the temperature T₁ may be detected by means of atemperature sensor such as a thermistor, thermocouple, or the like.Also, as described later, the change in temperature may be detectedbased on the change in the resistance value of the Hall element thatoccurs due to the change in temperature. In this case, such anarrangement does not require an increase in the number of components todetect the temperature of such an element itself for which thetemperature is to be detected.

In the operation 5, x₁ obtained in the operation 4 is assigned to thefunction y=a*x+b designed in the operation 2, so as to calculatey₂=a*x₁+b. This corrects the measurement value y₁ to y₂, therebyproviding linearity compensation. In this linearity compensation, evenin a case of the temperature T₁, the expression designed for thetemperature T₀ is employed. This leads to error due to the differencebetween the temperatures T₀ and T₁.

In the operation 6, the temperature compensation is performed so as tocorrect the aforementioned error. Specifically, temperature dependenceof the slope and the offset that represents a linear function iscorrected as represented by y₃=c*y₂+d. The coefficients c and d areparameters determined beforehand for each temperature. It is notnecessary to acquire the coefficients c and d for each individualproduct. Before the inspection step, preferably, the values may beappropriately determined based on a small number of typical samples(products). In a case in which the relation expression passes throughthe origin (i.e., b=0), this requires only slope correction. That is tosay, the operation may be performed assuming that d=0.

As described above, by performing both the linearity compensation andthe temperature compensation, this provides a constant relation havinglinearity between the position detection signal and the change inposition regardless of the temperature. In a state in which the positionprovided by the servo motor has settled, the position detection signalis equal to the position instruction value. Thus, the relation betweenthe position instruction value and the change in position is maintainedas a linear and stable relation regardless of temperature or individualvariation. That is to say, when a given position instruction valueP_(REF) is input, this allows the processor 306 to change the positionof the lens 304 to the same position regardless of temperature andvariation.

Specific description will be made with reference to the graphs in FIGS.5 through 8 regarding the measurement results and correction examples.

FIG. 5 shows an example of actual measurement results of the relationsbetween the position detection signal y₁ and the change in position x.The graphs 10 respectively represent the measurement results at thetemperatures 10° C., 15° C., and 35° C. From among the threetemperatures, two temperatures involve the largest change in themeasurement results. The remaining one involves an intermediate changein the measurement results, which is selected as a typical temperature.The vertical axis values for each graph vary depending on the gain ofthe Hall amplifier and depending on whether the values represent theoutput of the Hall element or the target code. Accordingly, absolutevalues are meaningless even assuming that the measurement resultsrepresented by the graphs are acquired under the same conditions. Thus,the values on the vertical axis are not shown. Each graph 10 is close toa linear function. In actuality, each graph 10 is curved. Furthermore,the curve of each graph has a slope that changes due to temperature.

FIG. 6 shows graphs showing the results obtained by performing thelinearity compensation (operations 4 and 5) for the results shown inFIG. 5. The function reference temperature T₀ is 25° C., which is notshown in the drawing. A fifth-order expression is designed so as torepresent the relation between the position detection signal y and thechange in position x measured at 25° C. As a result, the function x=f(y)is obtained. Next, the values of the position detection signal are inputto the function x=y(y) for each temperature. Furthermore, linearitycorrection is performed using the function f=a*x. Here, “a” represents aslope determined beforehand. Specifically, the slope “a” is defined as aslope that represents the relation between the position detection signaland the change in position at a temperature of 25° C., which is derivedin the vicinity of an intermediate position of the change in position.As represented by the graphs 11, the result for each temperature can becorrected and approximated as represented by an approximately linearfunction. However, linearity compensation is performed for all thetemperatures by means of a single function designed for 25° C. Thisleads to error due to this function. As a result, there is a differencein the slope between the temperatures.

FIG. 7 shows the results obtained by performing temperature slopecompensation for the results shown in FIG. 6 with the slope correctioncoefficients designed for respective temperatures. Specifically, thecorrection coefficient is designed for each temperature such that thecalculation result matches the linear function having a slope designedfor the reference temperature T₀, i.e., 25° C. The correctioncoefficient designed for each temperature corresponds to the coefficient“c” in the operation 6 shown in FIG. 2.

For example, description will be made with the slope for 25° C. asα_(25° C.), with the slope for 10° C. as α_(10° C.), with the slope for15° C. as α_(15° C.), and with the slope for 35° C. as α_(35° C.). In acase in which the graph data for 10° C. is multiplied byα_(25° C.)/α_(10° C.), the calculation result matches the graph data for25° C. Similarly, in a case in which the graph data for 15° C. ismultiplied by α_(25° C.)/α_(° C.), the calculation result matches thegraph data for 25° C. In a case in which the graph data for 15° C. ismultiplied by α_(25° C.)/α_(15° C.), the calculation result matches thegraph data for 25° C. In a case in which the graph data for 35° C. ismultiplied by α_(25° C.)/α_(35° C.), the calculation result matches thegraph data for 25° C.

Accordingly, in the operation 6 shown in FIG. 2, the correctioncoefficient c_(10° C.) for the temperature 10° C. is defined asα_(25° C.)/α_(10 ° C.)Similarly, the correction coefficient c_(15 ° C.)for the temperature 15° C. is defined as α_(25° C.)/α_(10° C.).Furthermore, the correction coefficient C_(35° C.). for the temperature35° C. is defined as α_(35° C0.)/α_(10 ° C).

The correction coefficients c_(10 ° C.), c_(15 ° C.), C_(35 ° C.). thusobtained may preferably be stored in the form of a table in memoryincluded in the lens control apparatus. When the detected temperatureobtained by a temperature detection means is an intermediate temperaturebetween two adjacent temperatures defined in the table (10, 15, and 35°C. in this example), an average of the two correction coefficientsdefined for the two adjacent temperatures between which the detectedtemperature is positioned may be employed. Also, the correctioncoefficient may be calculated by means of linear interpolation. Also,such correction coefficients may be held in the form of a function ofthe temperature. As shown by the graphs 12, the results subjected to thelinearity compensation and the temperature compensation are alignedalong almost a single straight line regardless of the temperature. Thismeans that, in the actual operation of the actuator driver IC 500, theposition detection signal y₃ obtained in the operation 6 indicates theactual position x with high precision

As viewed from the processor 306, the relation between the positiondetection value P_(REF)(y) and the actual position x of the lens xalways satisfies the relation expression y=a* x+b. This provides theoverall system with high-precision and high-speed positioning of thelens 304.

FIG. 7 shows an example in which the correction coefficients c for therespective temperatures are designed such that they are optimumcorrections for a small number of representative samples measured inactuality. However, each correction coefficient varies due to individualvariation. Accordingly, the optimum correction is not necessarilyobtained using the same correction coefficient. In order to solve such aproblem, an optimum correction coefficient may be designed beforehandfor each individual product. However, this requires temperaturecharacteristics measurement for every individual product, which leads toreduced productivity. In a case in which such individual variation isnon-negligible, the correction coefficient distribution may becalculated based on measurement results for multiple individualproducts, and specifically, an average thereof may be employed as a setvalue for the correction coefficient, for example. FIG. 8 shows theresults in a case in which slope correction is performed using such anaverage value of the correction coefficients. In this case, as shown ingraph 13, correction error occurs in the slope due to individualvariation of the correction coefficient. However, even in this case,such an arrangement provides reduced correction error as compared with acase in which no slope correction is performed (FIG. 6).

It should be noted that the flow shown in FIG. 2 is nothing more than anexample. That is to say, the present invention is by no means restrictedto such an example. Also, the order of the operations may be changed.For example, first, the slope correction may be performed for eachtemperature, which provides constant correction values represented by afunction having a non-linear component regardless of the temperature.Subsequently, a linearity operation may be performed using a singlefunction. FIG. 9 shows the results obtained by performing the slopecorrection for each temperature before the linearity compensation isperformed. This provides the correction results represented by afunction having a remaining non-linear component. However, thecorrection results are represented by almost a single curve regardlessof the temperature. That is to say, the results represented by such asingle curve are subjected to the linearity compensation using a singlefunction. This allows the linearity compensation to involve almost nofunction error. Thus, as indicated by the graphs 14, after the linearitycompensation, the results are represented by almost a single straightline. As described in this example, in a case in which such samples haverelatively high linearity, there is almost no difference in thecorrection result between the aforementioned two methods.

It should be noted that it is difficult to derive an optimum slopecorrection value and an offset correction value for the characteristicsrepresented by such a curve before the linearity compensation. In otherwords, as shown in FIG. 2, first, the linearity compensation ispreferably performed. Furthermore, offset correction is preferablyperformed in the linearity compensation (such that the calculatedresults pass through the origin, i.e., such that b=0 holds true). Afterthe linearity compensation, only the slope correction is preferablyperformed (assuming that d=0). This enables high-precision correction.Furthermore, this facilitates calculation of correction coefficients.Also, in some cases, the calculation results cannot be represented by asingle curve regardless of the temperature even if the slope correctionis performed for each temperature, and even if, in addition, the offsetcorrection is performed for each temperature. In such cases, in a caseof performing the linearity compensation after the temperaturecompensation, there is a difference in the slope of the linear functionbetween the temperatures. Accordingly, such an arrangement requiresadditional slope correction to be performed. In such cases, thetemperature correction is preferably performed after the linearitycompensation, which facilitates the correction operation.

Second Embodiment

Description will be made with reference to FIGS. 10 through 14 regardinga second embodiment of the present invention. FIG. 10 is a flowchartshowing temperature compensation and linearity compensation operationsof the lens control apparatus according to the second embodiment of thepresent invention. FIG. 11 shows the results obtained by performinglinearity compensation for the measurement results for the respectivetemperatures based on the relation between the position detection signaland the change in position for each temperature shown as the results inFIG. 5, and by performing temperature compensation such that there is nodifference in the slope between the temperatures.

The major difference in the flow between FIGS. 10 and 2 is that, in FIG.10, multiple functions are prepared based on the measurement resultsunder the respective multiple temperatures, and employed as a functionused for the linearity compensation. This allows the linearitycompensation to be performed using a function that represents thecharacteristics at the actual temperature or otherwise thecharacteristics at a temperature that is in the vicinity of the actualtemperature. This allows the linearity compensation to involve reducedfunction error, thereby providing reduced correction error.

In the operation 15, the relation between the position detection signaly and the change in position x is acquired for each of multiplepredetermined temperatures T₀, T₁, T₂, etc. As the number of settingtemperature conditions becomes large, function error due to deviationfrom the actual temperature can be reduced, which provides improvedcorrection precision. However, this involves an increased number ofadditional temperature measurement steps to be performed beforehand.Accordingly, the number of temperature conditions may be determinedgiving consideration to a tradeoff between the requested precision andthe costs required for such additional steps.

In the operation 16, a linear function y=a*x+b to be employed in thelinearity compensation is designed. That is to say, the slope “a” andthe intercept “b” are determined. In a case in which zero-pointadjustment is performed in the measurement, the measurement resultpasses through the origin, i.e., b=0. Thus, in this case, only the slope“a” may be derived. Here, description will be made regarding anarrangement in which the measurement results have the characteristics ofpassing through the origin as described in the first embodiment. Theslope “a” at the representative temperature T₀ is acquired. The sameslope is employed regardless the temperature. This provides temperaturecompensation at the same time as the linearity compensation.

In the operation 17, a function that represents the relation between themeasured position detection signal y and the change in position x isderived. In an actual machine such as a cellular phone, y represents ameasurement value. Accordingly, a function such as x=f(y) is designedwith y as a variable. In order to fit a nonlinear relation with such afunction, the function is required to have a second order or more. Asthe order is raised, the fitting error becomes smaller. However, thisinvolves an increase in the calculation amount. Accordingly, the ordermay preferably be designed according to the actual conditions. In thelinearity compensation described below, a fifth-order function isemployed. Such a function is designed for each of the measurementresults obtained beforehand for the respective temperatures.

In the operation 18, the position detection signal y₁ detected inactuality is assigned to such a function so as to obtain the calculatedchange in position x₁. When the surrounding temperature matches any oneof the temperatures T₀, T₁, T₂, and the like, the function designed forthe same temperature is used. In a case in which such a function is notprepared for the same temperature, the function designed for the closesttemperature condition is used. Alternatively, an additional function maybe generated by performing interpolation based on a pair of functionsdesigned for the adjacent temperatures between which the actualtemperature is positioned. In this case, it is difficult to generate acomplicated function. Accordingly, such an additional function may begenerated to have a slope obtained by averaging the slopes of the pairof functions.

In the operation 19, x₁ thus obtained in the operation 18 is substitutedinto the function y=a*x+b designed in the operation 16, therebyobtaining y₂=a*x₁+b. Thus, the measurement value y₁ is corrected to y₂,thereby providing linearity compensation. In the embodiment 1, after thelinearity compensation, the slope correction is performed as thetemperature compensation. In contrast, by employing the functiondesigned for each temperature, this allows the function error to bereduced. Furthermore, linearity compensation is performed employing thesingle slope “a” thus designed. This means that the slope correction isalso performed at the same time in the linearity compensation. It shouldbe noted that, in a case in which such optimum function data cannot beprepared, and accordingly, in a case in which the function error isnon-negligible, the slope correction may further be performed.

FIG. 11 shows graphs of the results obtained by performing the linearitycompensation for the results shown in FIG. 5. The reference temperaturevalues for which the aforementioned function is designed are the same asthe respective temperatures, i.e., 10° C., 15° C., and 35° C. Thefunction is designed in the form of a fifth-order expression so as torepresent the relation between the position detection signal y and thechange in position x measured at each of the aforementionedtemperatures. As a result, the function x=y(y) is derived for eachtemperature. Next, the values of the position detection signal are inputto the function for each temperature. Furthermore, linearity correctionresults are calculated based on the linear function y=a*x using thepredetermined slope “a”. The linearity compensation is performed usingthe same slope “a” regardless of the temperature. This also provides theslope correction at the same time as the linearity compensation. Theresults represented by the graphs 20 are represented by an almost singlestraight line regardless of the temperature. This allows the correctionerror to be further reduced as compared with the results shown in FIG.7. Because the linearity compensation is performed after theaforementioned function designed for the same temperature as the actualtemperature is applied, it is natural for the result to be a cleanstraight line. In actuality, there is a certain degree of differencebetween the actual temperature and the temperature condition under whichthe aforementioned function is designed, leading to an increase in thecorrection error. In a case in which improving the precision of thelinearity compensation and the temperature compensation involvesacceptable time and effort, the characteristics may preferably beprepared in the form of a database under as many temperature conditionsas possible.

Next, description will be made regarding an example of the linearitycompensation and the temperature compensation employed in the lenscontrol apparatus having different characteristics. FIG. 12 shows themeasurement results for explaining the change due to temperature in therelation between the position detection signal and the change inposition in the lens control apparatus having a relation that isdifferent from that shown in FIG. 5. FIG. 13 is a diagram showing theresults subjected to the slope correction and offset correction as thetemperature compensation before the linearity compensation is performed.FIG. 14 is a diagram showing the results obtained by performinglinearity compensation for the measurement results for the respectivetemperatures based on the relation between the position detection signaland the change in position for each temperature shown as the results inFIG. 13, and by performing temperature compensation such that there isno difference in the slope between the temperatures.

In FIG. 12, the graphs 21 show the results at the temperatures 5° C.,30° C., and 50° C., which indicate the difference in characteristics dueto temperature. From among the three temperatures, two temperaturesinvolve the largest change in the measurement results. The remainingtemperature involves an intermediate change in the measurement result,and is selected as a representative temperature. The major difference inthe results between FIGS. 12 and 5 is that the result shown in FIG. 12exhibits degraded linearity. Specifically, a large change occurs in theslope depending on the stroke range.

FIG. 13 shows the results obtained by performing the slope correctionfor the results shown in FIG. 12 for each temperature before thelinearity compensation. The offset correction is executed at the sametime as the slope correction. The results are converted such that theyare aligned along a graph passing through the origin. The graphs 22 havea remaining non-linear component. Furthermore, the calculation resultsdo not match for the respective temperatures. That is to say, in thisexample, the slope correction is effectively performed for the range inwhich the change in position is small. However, the slope correction isnot effective for the range in which the change in position is large. Inthis range, correction deviation occurs. That is to say, in a case inwhich such characteristics are to be corrected, satisfactory temperaturecompensation cannot be provided by performing only the slope correctionand the offset correction. Thus, in a case in which the result of such acorrection operation is subjected to the linearity compensation, thisleads to a large correction error.

In a case of correcting such characteristics, the linearity compensationis preferably performed for each temperature based on the function datacalculated for each temperature according to the flow shown in FIG. 10.FIG. 14 shows the results obtained by performing the linearitycompensation for each temperature using the functions designed based onthe measurement data acquired at the respective temperatures 5° C., 30°C., and 50° C., and by performing the slope correction for eachtemperature such that the calculation results are aligned along a linehaving the same slope. The graph curves 23 are represented by almost asingle straight line. This means that both the linearity compensationand the temperature compensation are provided.

Third Embodiment

Description will be made regarding a third embodiment of the presentinvention with reference to FIGS. 15 through 16. FIG. 15 is a flowchartshowing a temperature compensation operation and a linearitycompensation operation of the lens control apparatus according to thethird embodiment of the present invention. FIG. 16 is a diagram showingthe results obtained by performing the linearity compensation and thetemperature compensation under a condition in which the stroke range islimited.

In a case in which the characteristics exhibit poor linearity as shownin FIG. 12, by performing the linearity compensation for eachtemperature using the aforementioned function designed for thecorresponding temperature, this provides correction with relativelysmall correction error. However, such an arrangement requirespreparation of the functions designed for respective temperatures, whichrequires additional time and additional memory capacity. In order tosolve such a problem, FIG. 15 shows a flow showing another correctionmethod. The point of difference from the flow shown in FIG. 1 is asfollows. That is to say, after acquiring the relation between theposition detection signal and the change in position at thepredetermined temperature To, in a case in which judgment is made thatsatisfactory results of the linearity compensation and the temperaturecompensation cannot be obtained due to poor linearity, a particular partof the stroke range having poor linearity characteristics is omittedfrom the correction range. That is to say, the correction is performedfor only a stroke range in which satisfactory correction results can beobtained.

In the operation 24, the relation between the position detection signaly and the change in position x is acquired at the predeterminedtemperature T₀, e.g., at the set temperature of the factory.

In the operation 25, the range to be corrected is limited to a part ofthe stroke range that has been judged to be a range that can be used forthe control operation based on the results obtained in the operation 24.After the stroke range is limited, offset correction may be performedsuch that the limited stroke range includes the origin.

In the operation 26, the linear function y=a*x+b is designed along whichthe calculation results are to be aligned after the linearitycompensation. In a case in which the offset correction is performedbefore the operation 26, the input data passes through the origin, i.e.,b=0 holds true. Thus, in this case, only the slope “a” is derived.

In the operation 27, a function is designed so as to represent therelation between the position detection signal y and the change inposition x measured beforehand. In an actual machine such as a cellularphone, y represents a measurement value. Accordingly, a function such asx=f(y) is designed with y as a variable. In order to fit a nonlinearrelation with such a function, the function is required to have a secondorder or more. As the order is raised, the fitting error becomessmaller. However, this involves an increase in the calculation amount.Accordingly, the order may preferably be designed according to theactual conditions. In the linearity compensation described below, afifth-order function is employed.

In the operation 28, the position detection signal y₁ detected inactuality is assigned to the aforementioned function, thereby acquiringa calculated change in positon x₁. In a case in which the surroundingtemperature is equal to T₀, it can be assumed that the measurementresult matches the factory measurement result. Even in a case in whichthe surrounding temperature is T₁, which is different from T₀, thefunction x=f(y), which is designed for T₀, is also employed.

In the operation 29, x₁ obtained in the operation 28 is assigned to thefunction y=a *x+b designed in the operation 26, so as to calculatey₂=a*x₁+b. This corrects the measurement value y₁ to y₂, therebyproviding linearity compensation. In this linearity compensation, evenin a case of the temperature T₁, the expression designed for thetemperature T₀ is employed. This leads to error due to the differencebetween the temperatures T₀ and T₁.

In the operation 30, the temperature compensation is performed so as tocorrect such error. Specifically, the temperature correction isperformed by means of slope correction and offset correction of a linearfunction, thereby obtaining y₃=c*y₂+d. In a case in which the relationexpression passes through the origin, only the slope correction maypreferably be performed.

FIG. 16 shows the result obtained by performing the linearitycompensation and the temperature compensation under such a condition inwhich the stroke range is limited as described above. As shown in graphs31, this involves a small amount of correction error. However, thisprovides both linearity compensation and temperature compensation withhigh precision.

It should be noted that description will be made regarding anarrangement in which a part of the stroke range having poor linearity isomitted, and only the range to be used is shown on the graphs. However,in an actual apparatus, it is not always necessary to disable theoperation in such a stroke range having poor linearity, or otherwise todisable the output of the position detection signal for such a strokerange, and such linearity deviation or change in temperature may betolerated for such a range.

As described above, in a case in which it is difficult to obtainlinearity over the overall stroke region and to suppress the change dueto temperature, by securing linearity for predetermined positions or apredetermined stroke range so as to suppress the change due totemperature, this provides improved performance for at least such apredetermined stroke range. The positions or the stroke range for whichthe linearity compensation and the temperature compensation are to beoptimized may preferably be determined according to the purpose. Forexample, in a case of designing the linearity compensation and thetemperature compensation for an AF mechanism, and in a case in whichhigh priority is assigned to landscape photography, the linearitycompensation and the temperature compensation are preferably optimizedfor the infinity distance range. On the other hand, in a case in whichhigh priority is assigned to a self-portrait, the linearity compensationand the temperature compensation are preferably optimized for a lensposition range that corresponds to a subject distance on the order of 1m. In a case of designing the linearity compensation and the temperaturecompensation for an OIS mechanism, the linearity compensation and thetemperature compensation are preferably optimized for a range includingthe vicinity of a neutral position of a spring or a centering settingposition in a state in which no optical image stabilization is input.

Fourth Embodiment

Description will be made regarding a fourth embodiment of the presentinvention with reference to FIG. 17. FIG. 17 is a diagram for explaininga method for performing linear approximation of the function accordingto the fourth embodiment. Description has been made in the first throughthird embodiments regarding an arrangement in which, in a case in whichthe relation between the position detection signal y and the change inposition x at the predetermined temperature T₀ is non-linear, thecorrection operation is performed using a higher-order function, e.g.,fifth-order function. However, in a case in which the linearitycompensation is performed in an actual image capture apparatus withcalculation involved in such a fifth-order function, this requires along calculation time, and requires a large memory capacity for storingintermediate calculation results. In order to solve such a problem,after the range to be represented by the function x=f(y) is divided intomultiple sections, each section thus divided may be approximated by alinear function. This has the potential to involve a small amount ofdegradation in the calculation precision. However, in a case in which anactuator has x−y characteristics that vary smoothly, such linearinterpolation has almost no adverse effect. In a case of correcting thestroke range of an AF mechanism or an OIS mechanism of a typical cameramodule, the linear interpolation may preferably be performed byconnecting a sufficient number of representative points, the number ofwhich is on the order of 16 to 20. This provides satisfactory results

FIG. 17 shows the measurement points each represented by a solid circle,a higher-order function obtained by means of data fitting based on themeasurement points, which is represented by the broken line, and theapproximation result obtained by connecting adjacent representativepoints by a straight line, which is represented by the solid line. In acase in which the linear connection approximation is performed based ona sufficient number of measurement points, there is not a largedifference in the approximation result as compared with the higher-orderfunction approximation. In this case, a pair of an x value and a y valuefor each measurement point may preferably be stored in the form of acorrection table in memory. For the operation 5 or the like shown inFIG. 2, when the position detection signal y₁ is detected at a positionbetween the measurement points thus stored, the x₁ value may preferablybe calculated using the data of the adjacent measurement points thereof,and specifically, based on a linear function that connects the twomeasurement points.

An arrangement is conceivable in which the adjacent measurement pointsare connected without designing such a function. However, with such anarrangement, if the measurement result obtained at a givenrepresentative point has a serious noise component, i.e., if theselected representative point is a singular point, in a case in whichthe measurement points are directly connected by a straight line, thisresults in poor smoothness. It can be assumed that the actualcharacteristics smoothly vary as compared with the aforementionedexample. In order to solve such a problem, after a smoothly curvedfunction is designed so as to represent the measurement results, linearconnection approximation is preferably performed for the function thusdesigned. In designing the function, a function is preferably selectedso as to provide least mean square error with respect to the measurementpoints, instead of designing a function that passes through all themeasurement points.

Next, specific description will be made regarding an exampleconfiguration of the lens control apparatus 400.

FIG. 18 is a specific block diagram showing the lens control apparatus400. The position detector 404 is configured as a Hall element 32. TheHall element 32 generates a Hall voltage V₊, V⁻ that corresponds to thechange in the position of a movable portion of the actuator 402, andsupplies the Hall voltage to Hall detection pins (HP, HN) of theactuator driver IC 500.

A position detection unit 510 generates a digital position detectionvalue P_(FB) that indicates the position (change in position) of themovable portion of the actuator 402, based on the Hall voltage V₊, V⁻.The position detection unit 510 includes a Hall amplifier 512 thatamplifies the Hall voltage, and an A/D converter 514 that converts theoutput of the Hall amplifier 512 into the position detection valueP_(FB) in the form of a digital value.

A temperature detection unit 520 generates a temperature detection valueT that indicates the temperature. As described above, the temperaturedetection value preferably represents the temperature of the positiondetector 404. In FIG. 18, the Hall element 32 configured as the positiondetector 404 is also employed as the temperature detector 406. Such anarrangement is configured to make use of the fact that an internalresistance r of the Hall element 32 has temperature dependence. Thetemperature detection unit 520 measures the internal resistance r of theHall element 32, and uses the information that indicates thetemperature.

The temperature detection unit 520 includes a constant current circuit522 and an A/D converter 524. The constant current circuit 522 suppliesa predetermined bias current I_(BIAS) to the Hall element 32. The biascurrent I_(BIAS) is a power supply signal that is required to operatethe Hall element 32. Accordingly, the constant current circuit 522 canbe regarded as a Hall bias circuit.

A voltage drop I_(BIAS)×r occurs across the Hall element 32. The voltagedrop is input to a Hall bias pin (HB). The A/D converter 524 convertsthe voltage V_(HB) (=I_(BIAS)×r) applied to the HB pin into a digitalvalue T. The bias current I_(BIAS) is a known and constant current.Thus, the digital value T is configured as a signal that is proportionalto the internal resistance r. Accordingly, the digital value T includestemperature information with respect to the Hall element 32. Therelation between the internal resistance r and the temperature ismeasured beforehand. The relation thus measured is held in the form of afunction or otherwise a table. In the correction unit 530 configured asa downstream stage, the digital value T is converted into thetemperature information.

The interface circuit 540 receives, from the processor 306, a targetcode TC that indicates the target position of the movable portion of theactuator 402. For example, the interface circuit 540 may be configuredas a serial interface such as an I²C (Inter IC) interface. A filter 550filters the target code TC received by the interface circuit 540, andgenerates a position instruction value P_(REF). In a case in which theposition instruction value P_(REF) suddenly changes, this has thepotential to involve ringing in the position of the lens 304. Byproviding the filter 550, such an arrangement suppresses the ringing.

The correction unit 530 corrects the position detection value P_(FB)received from the position detection unit 510. Specifically, thecorrection unit 530 includes a linearity compensation unit 532, atemperature compensation unit 534, and memory 536. The linearitycompensation unit 532 corrects the linearity of the relation between theposition detection value P_(FB) and the actual position (theaforementioned x−y characteristic). The memory 536 stores theaforementioned parameters a and b, data that represent the functionx=f(y) (e.g., coefficients k₀ through k₅), parameters c and d, etc. Thememory 536 may be configured as nonvolatile memory such as ROM or flashmemory. Otherwise, the memory 536 may be configured as volatile memorythat temporarily stores data to be supplied from external ROM every timethe circuit is started up.

The temperature compensation unit 534 corrects the change in therelation between the position detection value P_(FB) and the actualposition that occurs due to the change in temperature.

For example, in the first embodiment, the operation of the linearitycompensation unit 532 corresponds to the operations 4 and 5 in theflowchart shown in FIG. 2. The operation of the temperature compensationunit 534 corresponds to the operation 6 in the flowchart shown in FIG.2.

In the second embodiment, the operation of the linearity compensationunit 532 corresponds to the operation 19 in the flowchart shown in FIG.10. The operation of the temperature compensation unit 534 correspondsto the operation 18 in the flowchart shown in FIG. 10.

In the third embodiment, the operation of the linearity compensationunit 532 corresponds to the operations 28 and 29 in the flowchart shownin FIG. 15. The operation of the temperature compensation unit 534corresponds to the operation 30 in the flowchart shown in FIG. 15.

The controller 560 receives the position instruction value P_(REF) and aposition detection value P_(FB) _(_) _(CMP) subjected to the correctionby means of the correction unit 530. The controller 560 generates acontrol instruction value S_(REF) such that the position detection valueP_(FB) _(_) _(CMP) matches the position instruction value P_(REF). In acase in which the actuator 402 is configured as a voice coil motor, thecontrol instruction value S_(REF) is an instruction value that indicatesa driving current to be supplied to the voice coil motor. The controller560 includes an error amplifier 562 and a PID controller 564, forexample. The error amplifier 562 generates a difference (error) ΔPbetween the position detection value P_(FB) _(_) _(CMP) and the positioninstruction value P_(REF). The PID controller 564 generates the controlinstruction value S_(REF) by means of a PID (Proportional IntegralDerivative) calculation. Instead of employing the PID controller 564, aPI controller may be employed. Also, a non-linear control operation maybe performed.

A driver 570 supplies a driving current that corresponds to the controlinstruction value S_(REF) to the actuator 402.

As can be understood from FIG. 18, the Hall voltage V₊, V⁻ is outputfrom the Hall element 32 via the terminals that differ from a terminalto which the control current is applied. That is to say, the change inthe resistance value of the Hall element 32 does not include a componentdue to the change in temperature and a component due to the change inposition in a mixed manner, unlike a shape memory alloy sensor. Thisprovides both the position detection and the temperature detection withhigh precision.

The operations of the correction unit 530 and the controller 560 may besupported by means of hardware components such as an adder, multiplier,etc. Also, such operations may be supported by means of a combination ofa CPU and a software program.

FIG. 19 is a diagram showing the temperature dependence of theresistance value of the Hall element. The solid circles represent themeasurement results. The broken line represents a linear approximationof the change in the measurement results. As described above, the changein temperature can be detected based on the change in the resistancevalue of the Hall element that occurs due to temperature. A constantbias current is applied to the Hall element, which allows a change inthe resistance value to be detected as a change in the bias voltage. Asshown in FIG. 19, the relation between the temperature and the Hall biasvoltage is approximately linear. Based on this result, it can beunderstood that the change in temperature can be detected by monitoringthe change in the bias voltage of the Hall element.

A notable feature is that the change in temperature of the resistor onthe bias side that is driven with a constant current is monitored in theform of a change in voltage, instead of monitoring the change in theoutput of the Hall element that occurs due to temperature. In a case inwhich the output voltage of the Hall element is monitored, this issubject to effects of the temperature characteristics of a Hallamplifier and to effects of the temperature characteristics of themagnetic flux density in addition to the temperature characteristics ofthe Hall element itself. Thus, it is difficult to purely detect only thechange in temperature. In contrast, in a case of monitoring the changein voltage on the bias side, the factor of the change due to thetemperature is mostly restricted to the change in resistance of the Hallelement. This allows the temperature to be detected.

It should be noted that description has been made with reference to FIG.18 regarding an arrangement in which the temperature detected by meansof the Hall element is used for the temperature compensation of therelation between the position detection signal and the actual position.However, the present invention is not restricted to such an arrangement.The detected temperature information may be used for abnormaltemperature detection, protection (thermal shutdown) accompanying anabnormal temperature state, or the like. Alternatively, the detectedtemperature information may be stored in a register so as to allow theCPU 306 to read out the detected temperature information thus stored.

The lens control apparatus as described above is employed in a cameramodule of a cellular phone or the like. In particular, one suitableapplication of the lens control apparatus according to the presentinvention is an image capture apparatus including an image sensor havinga phase difference detection means. The focusing deviation and thedeviation direction can be estimated based on the phase differencedetection results. Accordingly, by associating the phase differencedetection results with the position detection signal beforehand, such anarrangement is capable of estimating the amount of change in theposition detection signal required to change the position from thecurrent position to the focal position. Subsequently, the positionaccess operation is performed up to a target position indicated by acode of the position detection signal, thereby allowing the focal stateto be directly obtained. It should be noted that, with such anarrangement, linear calculation is performed in order to calculate theamount of change in the position detection signal required to change theposition up to the target position. Accordingly, in order to reduce theerror in position, it is important for the relation between the positiondetection signal and the change in position to have linearity. Inaddition, in a case in which the relation between them deviates due totemperature, the position deviates from the target position even afterthe current position is changed up to a position indicated by the codenumber that represents the target position. Accordingly, it is alsoimportant to support the temperature compensation. By applying thepresent invention, this provides both the linearity compensation and thetemperature compensation. Thus, the present invention is preferablyapplicable to an image capture apparatus including an image sensorhaving a phase difference detection means.

Another suitable application of the lens control apparatus according tothe present invention is an image capture apparatus mounting multiplecameras such as a dual camera. An application is conceivable that isconfigured to interlink the operations of the two cameras, and tocombine images captured by the two cameras so as to acquire a zoomimage, for example. In this case, the position detection signal is aninstruction to drive the lens positions of the two cameras in aninterlinked manner. In a case in which the interlinking between themdeviates due to temperature, this leads to a position error, and in somecases, this results in adverse effects on the image even aftercalibration is performed so as to secure such interlinking between themand the linearity compensation is performed. In particular, in a case inwhich there is a difference in the temperature characteristics betweenthe two cameras, it is needless to say that error occurs in aninstruction for changing the position to a given position. In addition,there is a difference between the amount of deviation between them.Thus, in a case in which the same temperature compensation is performedfor the two cameras, such an arrangement is not capable of providing ahigh-precision position control operation. By applying the presentinvention, such an arrangement provides both the linearity compensationand the temperature compensation. Furthermore, this allows suchcompensation to be executed for each camera. Thus, the present inventionis preferably applicable to an image capture apparatus mounting multiplecameras such as a dual camera or the like.

While the preferred embodiments of the present invention have beendescribed using specific terms, such description is for illustrativepurposes only, and it is to be understood that changes and variationsmay be made without departing from the spirit or scope of the appendedclaims.

What is claimed is:
 1. A lens control apparatus comprising: a lens; anactuator structured to position the lens; a Hall element structured togenerate a position detection signal that indicates a position of thelens; a temperature detection unit structured to detect a temperaturebased on a voltage across the Hall element in a state in which aconstant current is applied to the Hall element; and a control unitstructured to control the actuator such that the position detectionsignal approaches a position instruction signal that indicates a targetposition of the lens.
 2. The lens control apparatus according to claim1, wherein the control unit comprises a temperature compensation unitstructured to correct a temperature dependence of a relation between theposition detection signal and a corresponding actual position of thelens.
 3. The lens control apparatus according to claim 2, wherein thecontrol unit further comprises a linearity compensation unit structuredto correct a linearity of the relation.
 4. The lens control apparatusaccording to claim 3, wherein the relation is acquired at apredetermined temperature, wherein the control unit further comprises amemory structured to store information with respect to the relation,wherein the linearity is corrected for a current temperature thatdiffers from the predetermined temperature, based on the relationacquired at the predetermined temperature, and wherein temperaturecompensation is performed with a predetermined correction coefficientsupplied according to a difference between the predetermined temperatureand the current temperature.
 5. The lens control apparatus according toclaim 3, wherein the relations are acquired for a plurality ofpredetermined temperatures, wherein the control unit further comprises amemory structured to store information with respect to the relations,wherein the linearity is corrected for a current temperature thatdiffers from the predetermined temperatures, based on the relationacquired for one from among the plurality of temperatures that isclosest to the current temperature, and wherein temperature compensationis performed such that the relation is represented by a straight linehaving a slope that is unrelated to the temperature.
 6. The lens controlapparatus according to claim 3, wherein the relations are acquired for aplurality of predetermined temperatures, wherein the control unitfurther comprises a memory structured to store information with respectto the relations, wherein the relation is generated for the currenttemperature based on the relations acquired for adjacent temperaturesbetween which the current temperature is positioned, from among theplurality of predetermined temperatures, wherein linearity compensationis performed based on the relation thus generated, and whereintemperature compensation is performed such that the relation isrepresented by a straight line having a slope that is unrelated to thetemperature.
 7. An image capture apparatus comprising: a lens controlapparatus according to claim 1; and an image sensor that is capable ofperforming phase difference detection in order to support an autofocuscontrol operation, wherein temperature compensation and linearitycompensation are employed in detection of a position of the lens inorder to support an autofocus control operation.
 8. An image captureapparatus comprising a plurality of camera modules, wherein each cameramodule comprises the lens control apparatus according to claim 1, andwherein temperature compensation and linearity compensation are employedin detection of a position of the lens in order to support an autofocuscontrol operation for each camera module.
 9. An actuator drivercomprising: a position detection unit structured to generate a positiondetection value that indicates a position of a control target, based ona Hall signal generated by a Hall element; a correction unit structuredto correct the position detection value; a controller structured togenerate a control instruction value such that the position detectionvalue subjected to correction matches a position instruction value thatindicates a target position of the control target; a driver unitstructured to apply a driving signal that corresponds to the controlinstruction value to an actuator; and a temperature detection unitstructured to generate a temperature detection value that indicates atemperature based on a voltage across the Hall element in a state inwhich a predetermined current is supplied to the Hall element.
 10. Theactuator driver according to claim 9, wherein the correction unit isstructured to correct the position detection value such that therelation between the position detection value and an actual position isuniform regardless of the temperature in a range in the vicinity of aposition of the control target that corresponds to a predeterminedposition detection value.
 11. The actuator driver according to claim 9,wherein the correction unit is structured to correct the positiondetection value such that the relation between the position detectionvalue and an actual position exhibits a linearity that is uniformindependent of the temperature.
 12. The actuator driver according toclaim 11, wherein, with the position detection value or otherwise theposition instruction value as y, with the actual position as x, and withthe relation between x and y as an x−y characteristic, the correctionunit comprises memory structured to store data that represents the x−ycharacteristic y=a*x+b generated in the form of a linear function to beused as a calculation target, data that represents a function x=f(y)obtained by means of a polynomial approximation of the x−ycharacteristic measured beforehand at a predetermined temperature, andcorrection coefficients c and d (d may be set to zero) acquired for eachof a plurality of temperatures, wherein the correction unit isstructured to perform an operation comprising: calculating x₁=f(y₁) withthe position detection value received from the position detection unitas y₁; determining the coefficients c and d that correspond to thetemperature indicated by the temperature detection value; calculatingy₂=a*x₁+b; and calculating y₃=c*y₂+d, and wherein y₃ is employed as theposition detection value subjected to correction.
 13. The actuatordriver according to claim 12, wherein the function x=y(y) is dividedinto a plurality of sections, and wherein the function is approximatedfor each section in the form of a linear function.
 14. The actuatordriver according to claim 11, wherein, with the position detection valueor otherwise the position instruction value as y, with the actualposition as x, and with the relation between x and y as an x−ycharacteristic, the correction unit comprises memory structured to storedata that represents the x−y characteristic y=a*x+b generated in theform of a linear function to be used as a calculation target, and datathat represents a function x=f₀(y), x=f₁(y), and the like, obtained bymeans of a polynomial approximation of x−y characteristics measuredbeforehand at a plurality of predetermined temperatures T₀, T₁, and thelike, wherein the correction unit is structured to perform an operationcomprising: determining a function x=f′(y) that corresponds to thetemperature indicated by the temperature detection value; calculatingx₁=f(y₁) with the position detection value received from the positiondetection unit as y₁; and calculating y₂=a*x₁+b, and wherein y₂ isemployed as the position detection value subjected to correction. 15.The actuator driver according to claim 14, wherein the function x=y′(y)is divided into a plurality of sections, and wherein the function isapproximated for each section in the form of a linear function.
 16. Theactuator according to claim 9, monolithically integrated on a singlesemiconductor substrate.
 17. A lens control apparatus comprising: alens; an actuator comprising a movable portion on which the lens ismounted; and the actuator driver according to claim 9, structured toposition the actuator.
 18. An image capture apparatus comprising: animage sensor; and the lens control apparatus according to claim 17.